1. Field of the Invention
The present invention relates to the efficient heating of a device under test (DUT) without heating its environment, thereby allowing high temperature testing of the DUT in a conventional test handler.
2. Related Art
In a conventional semiconductor device, a package is formed around a chip. This package protects the chip and provides electrical leads, called pins, which can connect to bonding pads of the chip. During subsequent system integration, these pins can then be connected to portions of a printed circuit board.
The goal of semiconductor fabrication and packaging is to provide a device that can perform to specific parameters. Therefore, to ensure that a semiconductor device can operate properly before being integrated into a system, the semiconductor device is typically tested to verify its electrical and functional properties. A computer-controlled tester and a handler, typically performs these tests.
Specifications for many semiconductor devices can also include maximum operating temperatures. Unfortunately, high temperature testing currently requires an expensive isolation chamber within a handler where the semiconductor device can be heated, maintained at that temperature, and then tested. Typically, the heat transfer can be achieved by using a heating element in or forcing heated airflow through the isolation chamber. To ensure accurate testing, the temperature in the isolation chamber can be maintained at (or slightly above) a predetermined temperature. This high temperature isolation chamber is in addition to the handler, thereby significantly increasing testing costs.
To ensure a high temperature environment for the semiconductor device, certain components of the handler must also be placed inside the isolation chamber. Such components include the tracks for moving the semiconductor devices between staging trays as well as a clamping mechanism that secures and makes electrical contact with the leads of the semiconductor devices during testing. Because such components are placed in the same hostile environment as the semiconductor device, these components are more prone to failure, thereby further increasing the testing costs.
For these reasons, high temperature testing is generally not performed during the commercial production of standard semiconductor devices. In these cases, such devices are not guaranteed to pass temperature testing, although based on the particular fabrication and packaging processes used, most standard devices typically do pass. Semiconductor devices that have guaranteed specifications regarding temperature testing, e.g. thermometer chips or over-temperature sensors, are usually sold at a significantly higher price to offset the cost of the temperature testing.
However, increasingly more applications for semiconductor devices in, for example, laptops, notepads, etc. must withstand considerable heat for longer periods of time, thereby necessitating high temperature testing of such semiconductor devices. Therefore, a need arises for a high temperature testing technique that can be used with current non-temperature regulated test equipment.